This invention relates to irradiation specimen installation apparatus and more particularly to irradiation specimen installation apparatus including visual verification instrumentation.
In typical nuclear reactor power plant systems, the systems include a reactor vessel with a removable closure head mounted thereon. A plurality of fuel assemblies are disposed within the reactor vessel to form the reactor core so as to generate heat produced by the fissioning of the nuclear fuel. A coolant, such as water, is circulated through the reactor core which heats the coolant. The coolant flows through the remainder of the nuclear reactor system so as to produce steam in a manner generally understood in the art.
The fissioning of the nuclear fuel in the nuclear reactor core, not only exposes the fuel in the core to the radiation, but also exposes the internal structures of the nuclear reactor and the reactor vessel to the radiation generated by the core. The reactor vessel and internal support structures are designed for an extended lifetime, for example, 40 years. Over the course of this lifetime, these support structures and reactor vessel are exposed to a considerable amount of radiation. Therefore, it is important to be able to determine the radiation exposure of the various components of the nuclear reactor so that the life expectancy of the various components can be determined. Since the radiation flux from the nuclear reactor may vary with location in the core and vary along the circumference of the core, readings must be taken at various locations with respect to the core in order to have an accurate determination of the radiation exposure of the various components of the nuclear reactor.
In some nuclear reactors, radiation specimen containers are provided at various locations around the periphery of the core so as to provide locations wherein radiation specimens may be held. The radiation specimen disposed in the specimen container is thereby exposed to the radiation flux from the core at various locations around the core. During refueling of the nuclear reactor, the reactor closure head and various components of the upper internals of the reactor can be removed so as to expose the specimen containers. In this manner, radiation specimens can be removed or inserted in the specimen containers. When a radiation specimen is removed from the specimen container during the refueling process, the radiation specimen may then be examined to determine the radiation flux that that portion of the reactor vessel has experienced. At this time, the radiation specimens may also be rearranged so that the radiation specimens can be exposed to various levels of radiation at various locations around the core. In addition to determining the radiation exposure of the various components of the nuclear reactor, the radiation specimens can also be used to expose various elements to the radiation of the nuclear reactor. This can be done for test purposes such as determining the behavior of a particular kind of metal in the reactor environment.
In certain types of nuclear reactors, it is not possible for working personnel to view the specimen container from the top of the reactor vessel during the refueling process. In this type of reactor, the process of inserting the radiation specimen in the specimen container can be a difficult process due to the lack of visual verification of the insertion of the radiation specimen in the specimen container. This is important because should the radiation specimen be released when the radiation specimen is not in the specimen container, the radiation specimen may fall into the lower part of the reactor. Retrieval of a loose radiation specimen from the bottom of the reactor vessel is a difficult and expensive operation because most of the reactor internals including the core must be removed in order to access the loose irradiation specimen. Therefore, it is important to be able to positively place the irradiation specimen in the specimen container and to verify the placement of the radiation specimen before the specimen is released by the instrumentation. In this manner, the radiation specimen may be placed in the specimen container without the possibility of dropping the radiation specimen into the reactor vessel.
There now exist in the prior art numerous kinds of instrumentation for removing and inserting the radiation specimen with respect to the specimen container. For example, one such instrument is similar to the one described herein, however, that instrument does not have the capability of visually verifying that the radiation specimen has been positively inserted in the specimen container.
In addition to apparatus for installing and removing radiation specimens from specimen containers, separate apparatus exists for visually inspecting various components of the nuclear reactor. For example, U. S. Pat. No. 3,764,736 to Kosky et al. describes a remote visual examination apparatus for viewing reactor internals having a television camera with a self-contained lighting system that is capable of being placed in openings in the reactor core barrel flange for examining reactor internals. However, the Kosky et al device along with other apparatus generally known in the art, are not capable of being used together with installation and removal apparatus for radiation specimens in certain situations wherein accessibility of the specimen container is extremely limited.
Therefore, what is needed is irradiation specimen installation apparatus that is capable of installing or removing a radiation specimen from a specimen container and visually verifying the location of the radiation specimen in situations wherein accessibility to the specimen container is extremely limited.